Distinct axo-somato-dendritic distributions of three potassium channels in CA1 hippocampal pyramidal cells.
Bottom Line: The Kv2.1 subunit was found in somatic, proximal dendritic and AIS plasma membranes at approximately the same densities.A quasi-linear increase in the Kir3.2 subunit density along the dendrites of PCs was detected, showing no significant difference between apical dendritic shafts, oblique dendrites or dendritic spines at the same distance from the soma.Our results demonstrate that each subunit has a unique cell-surface distribution pattern, and predict their differential involvement in synaptic integration and output generation at distinct subcellular compartments.
Affiliation: Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony Street 43, Budapest, Hungary.Show MeSH
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Mentions: Using SDS-FRL, we detected immunogold labelling for the Kv2.1 subunit on P-face membranes, as expected from an antibody that recognises an intracellular epitope (aa. 837–853). Strong Kv2.1 immunoreactivity of PC somata and proximal dendrites was observed (Fig. 4A–F). The labelling consisted of scattered and clustered gold particles in the plasma membrane (Fig. 4B and F). Some of the Kv2.1-positive gold clusters were located over loose patches of IMPs, which might be GABAergic perisomatic synapses. To molecularly identify GABAergic synapses, we performed double-labelling experiments for Kv2.1 and NL-2, a specific marker of inhibitory synapses (Fig. 4C and D). These reactions revealed that the Kv2.1 subunit was absent from NL-2-containing areas, but occasionally the Kv2.1- and NL-2-positive clusters were close to each other. The non-uniform distribution of gold particles labelling for the Kv2.1 subunit was also characteristic for AISs (molecularly identified with either Nav1.6 or Kv1.1; Fig. 4I–L), where Kv2.1 clusters never overlapped with presumed axoaxonic synapses (Fig. 4J and L) and also showed a segregation from the Nav1.6 (Fig. 4I and J) and Kv1.1 (Fig 4K and L) labelling. Distal apical dendrites (Fig. 4G and H), oblique dendrites, dendritic spines and axon terminals rarely contained any gold particles.
Affiliation: Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony Street 43, Budapest, Hungary.